Incoming and Outgoing Messages are not equal when producing and consuming a single message

[Joshua Phelps]

Description

I am running the Python sample under quickstart and observing Incoming Messages and Outgoing Messages in Azure Monitor. When I send a single message, the Incoming Messages metric is 1 but Outgoing Messages shows 2. When I send more than one message, the metrics are equal. I am trying to understand why they are out of sync for a single message.

I don't see this behavior when not using the Kafka protocol for Event Hubs.

How to reproduce

1. Create an Event Hub with a single partition under the Standard pricing tier
2. Run the sample under quickstart/python and produce and consume a single message.
3. Observe the metrics in Azure Monitor

Has it worked previously?

I noticed this behavior a few months ago and validated it again today. I'm unsure if this has always been the case.

Checklist

IMPORTANT: We will close issues where the checklist has not been completed or where adequate information has not been provided.

Please provide the relevant information for the following items:

• [ x] SDK (include version info): confluent-kafka 1.9.2
• [ x] Sample you're having trouble with: Python quickstart
• [ x] Kafka client configuration: I did not modify the sample configuration other than adding the connection string, namespace and ssl.ca.location
• [ x] Namespace and EventHub/topic name: jtpeventhub/topic1
• [x ] Operating system: 18.04.1-Ubuntu
• Pricing tier: Standard